dlab gmbh ch-8400 winterthur physikalisch-meteorologisches observatorium davos dara the new...

dlab GmbHCH-8400 Winterthur

Physikalisch-Meteorologisches Observatorium Davos

DARA

The new Three-Cavity Digitally- Controlled Radiometer for Space

Application



Features

• 3 independently controllable cavities• Offers several open/close measurement sequences• Independent PID controllers for closed and open shutter

state• ~20 bit data acquisition for each I, U and PWM channel• Measurement period down to a few seconds• Uncorrelated sinus carrier for thermal error signal• Convex cavities with minimal dynamic

“Non-Equivalence”• Very fast shutter speed (one step)• Two data analysis methods were available

– Tail Integration Method (TIM)– Phase Sensitive Analysis (PSA)



Overview

ADC

PSA

Open/Close

DARA Instrument

Shutter C

Modulated Dual H-Bridge

Control

PWM

BlackBody A

BlackBody B

BlackBody C

DAC

Sun Irradiation

Shutter BShutter A

DMod

ADC

InMatrix

OutMatrix

PWM

PWM

DMod

TIM

DACSin LUT

PID

PID

ADC

ADC

ADC

PowerMeasure



3 Cavity Design



Thermal Simulation



Instrument Geometry

A) Precision Aperture B) Cavity, Aeroglaze Z302 Coating C) Heat Sink D) Thermal Resistor E) Thermometer F) Electrical Heater G) Radiation Shield H) ShutterI) View Limiting Aperture



Design Goals

• Reduce dynamic & static „Non-Equivalence“

• Reduce the number of Bonds

• New Aperture Geometry

• Reduce Stray Light

• Remove uncertainties due to “Aperture Warming”



Sinus Carrier for Thermal Balancing

0 0.02 0.04 0.06 0.08 0.1-1.5

-1

-0.5

0

0.5

1

1.5

Time [s]

Am

plitu

de [

1]

Time Signals

PWM 21.1%, 20 Hz

Sine 10 Hz

12Sin PWMf f n

• Decoupling from PWM by using an uncorrelated sine carrier

• Means fSin is not an overtone of fPWM

• fPWM = 20 Hz, fSin = 1010 Hz 0 200 400 600 800 1000 12000

0.05

0.1

0.15

0.2

0.25

Frequency [Hz]A

mpl

itude

[1]

Frequency Spectrum

PWM 21.1%, 20 Hz

Sine 1010 Hz

CBA

sin+ sin-

Demod

Error 1ADC

AN1+

AN1-

AN2+

AN2-

SPI

Demod

Error 2ADC

AN1+

AN1-

AN2+

AN2-

SPI

D1

D2

Thermistor Heater

Thermistor Sink



PID Controller Switching

z-1

z-1

z-1

e[n]

KP

KPTA

KD/TA

y[n]

2

• How can the settling time be reduced when changing the shutter state?

• Two PID controllers per channel

• Significantly less settling time is needed

• Measurement period can be reduced

PWM Duty Cycle with one PID

Shutter Closed Shutter Open Shutter Closed Shutter Open

PWM Duty Cycle with two PID’s

time



Power Measurement and Sampling

RS

Heater ADCAD7710

DACMAX5134

S&H

AN1+

AN1-

AN2+

AN2-

SPI

SPI

RH

PWM1

PWM0

US

UH

IS

• PWM frequency:20 Hz

• Duty cycle resolution 19.9 bit

• The heater current can be set by a DAC

• The effective heater current is measured by a 20 bit ADC

• Heater voltage is sampled when PWM is high and measured by a 20 bit ADC

Time

PWM0

PWM1

tsptdhtdh

[ ] [ ] [ ] SPWM H

S

UP n n U n

R



TIM Measure

PWMDuty Cycle

TIM Function

TIM-Window

TIM-Window

TSI Sampling

4: 2

nd

Pha

se

Mea

sure

2: 1

st

Pha

se

Mea

sureMeasurement

Turn

4: 2

nd

Pha

se

Mea

sure

2: 1

st

Pha

se

Mea

sure

4: 2

nd

Pha

se

Mea

sure

2: 1

st

Pha

se

Mea

sure

0 N

PS[0]

T TT

Shutter Closed Shutter Open Shutter Closed Shutter Open Shutter Closed Shutter Open

• Tail Integration Method or Traditional Irradiation Measure• The tail data are integrated• The sun power is calculated as the difference of 2

measurements made with closed shutter and 1 with open shutter

• One measure per open/close turn

/ 2 1 1 / 2 1

/ 2 / 2

[ ] 2 [ ] [ ]N N

Sn N T n T n N T

P P n P n P n

s WRR Ap SI C W P



PSA Measure

PWMDuty Cycle

SynchronousSinus

PSA-Window PSA-Window

PSA-Window PSA-Window

TSI Sampling

Shutter Closed Shutter Open Shutter Closed Shutter Open Shutter Closed Shutter Open

4:

2n

d

Ph

ase

M

ea

sure

2:

1st

P

ha

se

Me

asu

reMeasurement Turn

4:

2n

d

Ph

ase

M

ea

sure

2:

1st

P

ha

se

Me

asu

re

4:

2n

d

Ph

ase

M

ea

sure

2:

1st

P

ha

se

Me

asu

re

0 N

PS[1]PS[0]

• Phase Sensitive Analysis Measure• Heater PWM signal is weighted by a synchronous sine

signal• All data are taken into account for the analysis• Two measures per open/close turn

/ 4 1 12

3/ 4

3/ 4 1 12

/ 4

[0] [ ]sin 2

[1] [ ]sin 2

N

Sn N

N

Sn N

nP P n

N N

nP P n

N N

s WRR Ap SI C W P



Data Management

DARARS422

EGSE

SatelliteHost

• RS422 communication• Robust communication

protocol• EGSE software for data

visualization and data storage



First Measurements

7 8 9 10 11 12 13 14 15 16 17600

650

700

750

800

850

900

950

1000

1050

1100Irradiance, 21-Sep-2010

time(UTC-1) [h]

Irra

dian

ce [

W/m

2]

Cavity 1

Cavity 2

7 8 9 10 11 12 13 14 15 16 170.98

0.985

0.99

0.995

1

1.005

1.01

1.015

1.02Ratio to WRR(PMO2), 21-Sep-2010

time(UTC-1) [h]

Rat

io t

o W

RR

(PM

O2)

Cavity 1

Cavity 2

Not characterized yet!



First Measurements

7 8 9 10 11 12 13 14 15 16 170.98

0.985

0.99

0.995

1

1.005

1.01

1.015

1.02Ratio Cavity1/Cavity2, 21-Sep-2010

Rat

io C

avity

1/C

avity

2

time(UTC-1) [h]

11.978 11.98 11.982 11.984 11.986 11.988 11.99 11.992 11.994

0.2

0.3

0.4

0.5

0.6

0.7

PWM Signal, 21-Sep-2010

time(UTC-1) [h]

PW

M

Ratio Cavity A/Cavity C PWM Signal



IPC Results



Outlook

• Characterization (Ground & Space)

• Visit Calibration Facilities

• Verify WRR Scale

• SuMo Instrument on PROBA III (2015?)

dlab gmbh ch-8400 winterthur physikalisch-meteorologisches observatorium davos dara the new...

Documents

data visualization

data acquisition

closed shutter

steptwo data analysis

open shutter state

pwm channelmeasurement

aperture warmingsinus

thermal balancingdecoupling